docs: def _releaseId(self, msgId):
          """
          Release message ID to the pool.
  
          @param msgId: message ID, no longer on the wire
          @type msgId: C{str}
          """
          self._uuids.append(msgId)
          if len(self._uuids) > 2 * self.UUID_POOL_GEN_SIZE:
              self._uuids[-self.UUID_POOL_GEN_SIZE:] = []